English

Embedding calculus and Vassiliev spectral sequence

Algebraic Topology 2025-10-21 v2 Geometric Topology

Abstract

Vassiliev spectral sequence and Sinha spectral sequence are both related to cohomology of the space of long knots RR3\mathbb{R}\to \mathbb{R}^3. Although they have different origins, the Vassiliev E1E_1-page and the Sinha E2E_2-page are isomorphic (up to a degree shift). In this paper, we prove that they have isomorphic EE_\infty-pages if the coefficient ring is a field. Together with degeneracy of the Sinha sequence, this implies that the Vassiliev sequence degenerates at E1E_1-page over Q\mathbb{Q} including the non-diagonal part. Our result also implies that for any coefficient field, the space of finite type nn knot invariants is isomorphic to the space of weight systems of weight n\leq n if and only if the parts of the Sinha sequence of bidegree (i,i)(-i,i) degenerate at E2E_2 for i2ni\leq 2n. For the construction of the isomorphism, we use a variant of Thom space model which was introduced in the author's previous paper and captures embedding calculus of the knot space in terms of fat diagonals. As a byproduct of the construction, we give a partial computation on differentials of unstable versions of the Vassiliev sequence which converge to finite dimensional approximations of the knot space.

Cite

@article{arxiv.2509.23766,
  title  = {Embedding calculus and Vassiliev spectral sequence},
  author = {Syunji Moriya},
  journal= {arXiv preprint arXiv:2509.23766},
  year   = {2025}
}

Comments

48 pages, 3 figures, v2: Modified Corollary 1.4 (1) in v1 since its proof included an error. Removed (2) of the corollary as it follows from known diagonal collapse. Modified Conjecture 7.4. Also corrected minor errors

R2 v1 2026-07-01T06:02:17.389Z